Bendamustine having the structural formula
is a nitrogen mustard belonging to the family of drugs called alkylating agents. Bendamustine has been shown to be effective in the treatment of chronic lymphocytic leukemias and lymphomas. Bendamustine is normally used in its hydrochloride salt form as active agent. However, efficacy in terms of cytotoxicity and/or cytostaticity is a challenging issue and a critical problem.
US 2012/0003305 A1 and WO 2011/151086 A1 disclose pharmaceutical compositions of bendamustine or derivatives thereof for oral administration which comprise a pharmaceutically acceptable ingredient in the form of non-ionic surfactant(s) selected from the group consisting of polyethoxylated castor oil or derivatives thereof and block copolymer of ethylene oxide and propylene oxide, wherein in the compositions of WO 2011/151086 A1, alternatively to the aforementioned non-ionic surfactant(s), the pharmaceutically acceptable ingredient may be saccharide(s) selected from the group consisting of monosaccharide(s), disaccharide(s), oligosaccharide(s), cyclic oligosaccharide(s), polysaccharide(s) and saccharide alcohol(s). These non-ionic surfactant(s) or saccharide(s) are added to the pharmaceutical composition in order to avoid or reduce degradation of bendamustine in the form of the free acid within the pharmaceutical composition, and in particular to avoid degradation in the small or large intestine after uptake of bendamustine in order to improve its bioavailability. Besides the typical undesired degradation products of bendamustine in the form of the free acid, namely [5-[(2-chloroethyl)-(2-hydroxyethyl)amino]-1-methyl-benzimidazo-2-yl]-butanoic acid, 4-[5-Bis(2-hydroxyethyl)amino]-1-methylbenzimidazol-2-yl]-butanoic acid and 4-(5-morpholino-1-methylbenzimidazol-2-yl)-butanoic acid, for formulation purposes, bendamustine may also be present in the form of esters with sugar alcohols and C1-C6 alkyl alcohols.
WO 2010/042568 A1 discloses the preparation of pure bendamustine methyl ester
as starting material for the preparation of bendamustine hydrochloride.
CN 10169359 A discloses a process for preparing bendamustine hydrochloride in which bendamustine ethyl ester is obtained in form of a crude product which is further converted without purification. WO 2009/120386 A2 discloses a process for preparing bendamustine hydrochloride in which bendamustine ethyl ester is used as the starting material, wherein the document remains silent on preparation and purity of the applied bendamustine ethyl ester.
WO 2011/079193 A2 discloses the preparation of pure bendamustine isopropyl ester as starting material for the preparation of bendamustine hydrochloride.
A. M. Scutaru et al., “Bivalent bendamustine and melphalan derivatives as anticancer agents”, European Journal of Medical Chemistry, Vol. 46 (2011), pages 1604 to 1615 mainly focus on a concept of bivalent drugs and in this content show cytotoxicity data for maleimide-coupled bivalent bendamustine compounds comprising two moieties derived from bendamustine ester formed with N-(2-hydroxy-ethyl)maleimide. These bivalent bendamustine compounds are compared with bendamustine and a monovalent bendamustine ester formed with N-(2-hydroxy-ethyl)maleimide.
M. Scutaru et al., “Optimization of the N-Lost Drugs Melphalan and Bendamustine: Synthesis and Cytotoxicity of a New Set of Dendrimer-Drug Conjugates as Tumor Therapeutic Agents”, Bioconjugate Chem., 2010, 21, pages 1728 to 1743 disclose among others that modification of bendamustine with an N-(2-hydroxyethyl)maleimide spacer increases the hydrolytic stability of the N-lost moiety of bendamustine. There is still a need for bendamustine derivatives, and thus an object of the present invention is to provide bendamustine related compounds with useful properties and therapeutical effects, and therapeutical uses thereof.